Fluorinated organic acids



United States Patent 3,202,706 FLUORINATE'D ORGANIC ACIDS Murray Hauptschein, Glenside, and Robert E. ()esterling,

Flourtown, Pa., assignors to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Filed Aug. 4, 1961, Ser. No. 129,239 9 Claims. (Cl. 260-535) This invention relates to new fluorinated u-hydroxy carboxylic acids.

The new compounds of the invention are those of the general formula RCF OH(OH)COOH, and their metal salts and ammonium salts. In the above formula, R may be fluorine, or a perfluoroalkyl, a perfluorohydroalkyl, a perfluorochloroalkyl or a perfluorochlorohydroalkyl radical. As used herein, perfluoro means a radical containing only fluorine and carbon. Per-fluorohydro means a radical containing only carbon, fluorine and hydrogen in which the molar ratio of fluorinezhydr-ogen is at least 1:1. A perfluorochloro radical means one containing only carbon,fluorine and chlorine in which the molar ratio of fluorinezchlorine is at least 1:1. A perfluorochlorohydro radical means one containing only carbon, fluorine, chlorine and hydrogen in which the molar ratio of fluorine to chlorine plus hydrogen is at least 1:1. Where R is a fluorinated alkyl as defined above, it may contain from 1 to 20 carbon atoms and preferably from 2 to 12 carbon atoms.

A particularly preferred class of the fluorinated a-hydroxy acids of the invention are those in which R is a perfluoro radical having from about 2 to 12 carbon atoms. Another particularly preferred class are those of the formula R'[CH CF ],,CH(OH)COOH where R is a perfluoroalkyl or a perfiuorochloroalkyl radical and where n is an integer having a value of aboutone to eight. As explained hereinafter, this latter class of whydroxy acids may be prepared from telomers of vinylidene fluoride.

The new fluorinated a-hydroxy acids of the invention may be prepared by the reaction of terminal 'olefins of the formula RCH=CF where R is as defined above, with dinitrogen tetroxide (N 0,) at moderately elevated temperatures of from 50 to 150 C. and preferably from 80 to 130 C. The product of this reaction is then hydrolyzed in water or a mildly alkaline aqueous medium to provide the hydroxy acid RCI-I(OH)COOH. Al-

. though the invention does not depend upon any particular reaction mechanism, it is probable that the reaction of the olefin with N 0 and subsequent hydrolysis proceeds in accordance with the following:

(a) ON=O (b) ON=O (E hydrolysis R HCF3ON O VRCH(OH)OOOH According to the above, two nitrite groups add across the double bond to give, the dinitrite of Equation a. Upon hydrolyis, the nitrite group attached to the hydrogen containing carbon is hydrolyzed'to hydroxyl, While the nitrite group attached to the fluorinated carbon also hydrolyzes to hydroxyl to form the unstable difluoroalcohol RCH(OH)CF OH which in turn splits out hydrogen fluoride to form the acyl fluoride o 'RCH(OH)(UJF which finally hydrolyzes in the aqueous media to form the carboxylic acid ROH(OH)COOH (or a salt thereof in the presence of base; [The dinitrate, rather than the dinitrite as shown in Equations a and b may be the intermediate product in whole or in part due to the oxidizing conditions of the reaction. The dinitrate would hydrolyze in the same manner.]

In the above procedure, a second reaction occurs concurrently with that forming the hydroxy acid producing a nitro alcohol as a second major product. This second reaction probably occurs through the formation of a nitro-nitrite addition product which upon hydrolysis yields an a-hydroxy nitro compound according tothe following:

The fluorinated nitro alcohols produced by such reactions are believed to'be novel compounds and are the subject of the copending application of Murray Hauptschein and Robert E. Oesterling, Serial No. 128,646, filed August 2,1961. V r 1 Since the reaction temperatures are well above the boiling point of N 0 (about 20 C.), the reaction ,will take place at moderate superatmospheric pressures corresponding to the autogenous pressures'of the reactant at the reaction temperatures, generally ranging from 50 to 500 lbs./in. Reaction time is not critical. Generally, reaction periods are from 1 to 50 hours and preferably from 5 to 20 hours are satisfactory. The molar ratios of the reactants are not .critical, but it is preferred to use a molar excess of N 0 toinsure good conversions of the olefin to the addition product. Molar ratios of N 0 :olefin of from 1.1:1 to 1.5 :1 are generally preferable.

The reaction is desirably carried out in the presence of a solvent whichis unreactive to N 0 under thercaction conditions. Without a solvent, the addition reaction is difficult. to control, yields are lower, and explosion may occur. Preferred are the halogenated solvents, particularly the chlorinated or chlorofluorina-ted solvents such as chloroform, methylene chloride CH Cl carbon tetrachloride, trichlorotrifluoroethane, dichlorotetrafluoroethane etc. The amount of solvent is not critical and generally may be used in an amount ranging from to 1000 milliliters per mole of olefin. Desirably, the reaction is carried out under substantially anhydrous conditions to avoid reactions between N 0 and water and the possibility of other side reactions.

As is well known dinitrogen tetroxide (N 0 is probably an equilibrium mixture of N 0 with various other forms of nitrogen oxides particularly N0 whose com position changes depending principally upon temperahim. This behavior of N 0 is described for example, by I. L. Rebsomer in Chemical Reviews, vol. 36, No. 2, April 1945, pages 157 et seq, As used herein, the term dinitrogen tetroxide (N 0 is intended to include the various equilibrium mixtures that are obtained under the reaction conditions specified herein.

Recovery of thehydroxy acid following hydrolysis, and separation from the nitro alcohols concurrently produced, is conveniently eifected by performing the hydrol ysis in an aqueous alkaline media or by neutralizing the aqueous mixture following hydrolysis with a relatively mild base such as sodium carbonate or sodium bicarbonate. Upon neutralization, the nitro alcohols will generally separate as an insoluble organic layer, with the hydroxy acids contained principally in the aqueous layer in the salt form. The acid itself may be recovered from the aqueous layer by acidification e.g. with HCl followed compounds.

where n is an integer.

3 if necessary by extraction with an organic solvent such as diethyl ether.

Many of the precursor olefins RCH=CF are novel These may be prepared by the reaction of an iodide RI, where R is as defined above with vinylidene fluoride in accordance with the following:

Telomerization reactions of this type are described by Hauptschein et al. [JACS, vol. 80, pages 846 to 851] and in US. Patent 2,975,220 of Hauptschein et al. As described more in detail in these references, the reaction of the iodide with vinylidene fluoride is preferably carried out at elevated temperatures in the range of from about 20 to 250 C. and at elevated pressures. By using an excess of telogen R1, the reaction may be controlled to give yields of the 1:1 adduct of iodide to olefin, i.e. compounds of the type RCH CF I.

The iodides thus produced may then be dehydroiodinated by reaction with an ionic halide, e.g. lithium chloride, in a polar solvent, e.g. dimethylformamide. Such procedures are described in detail in the copending application of Murray Hauptschein et al., Serial No. 53,878

now Patent No. 3,116,337, filed September 6, 1960. Where the precursor iodide contains one vinylidene fluoride unit, olefins of the formula RCH=CF are obtained. Where the precursor iodide contains two or more repeating vinylidene fluoride units, the olefins produced by dehydroiodination will have the formula Typical examples of precursor olefins and the a-hydroxy acids that are obtained therefrom in accordance with the invention are the following:

mm. Hg.

according to the procedures described in the above mentioned copending application Serial No. 53,878. A 46.4 gram (0.2 mole) portion of the olefin is added to 100 milliliters of CFCl CF Cl and the resulting solution cooled to 0 C. Into this solution there is condensed 27.6 grams (0.3 mole) of dinitrogen tetroxide (N 0 and the mixture is then dried over P 0 at 0 C. for two or three hours. The solution is then filtered into a 300 milliliter stainless steel autoclave chilled to -10 C. which is then sealed and heated at 100 C. for 16 hours with agitation. The autoclave is then cooled in an ice bath and the contents transferred to a 200 milliliter Vigreaux still. The excess dinitrogen tetroxide and chlorofluorinated solvent are distilled from the mixture leaving grams of a yellow oil.

This product is then stirred with 200 milliliters of water at room temperature and sodium carbonate is then added to the mixture until it is slightly on the alkaline side. The

mixture is then allowed to separate into a water layer and a water insoluble layer consisting of a pale yellow oil. The

alkaline aqueous layer is then extracted twice with 40 milliliter portions of diethyl ether after which it is acidified by the addition of dilute hydrochloric acid. The acidified water layer is then extracted three times with 40 milliliter portions of diethyl ether. The ether extract is dried over anhydrous magnesium sulfate and evaporated giving 10 grams (20% yield) of a pale yellow oil which cystallizes on standing over night. Recrystallization from a benzenelight petroleum ether solvent gives colorless needles of the pure hydroxy acid CF CF CF CH(OH)COOH having a melting point of 108 to 109 C. boiling point 70 C. at 27 The infrared spectrum of this compound is characteristic of hydroxy acid absorption and consistent with the above structure. This compound is a strong acid.

Precursor Olefin a-hydroxy acid The a-hydroxy acids of the invention may be readily converted by conventional procedures into their metal salts and their ammonium salts. Thus, the alkali metal.

salts such as sodium, potassium, lithium etc., and other salts such as the calcium, magnesium, copper, iron, aluminum, chromium etc. salts may be produced by reacting the acid with the corresponding carbonate of the metal. The ammonium salts may be prepared readily by bubbling gaseous ammonia through a solution of the acid in a sol- 'vent such as diethyl ether or a fluorinated solvent such as CFCl CF Cl. The insoluble ammonium salt precipitates and is recovered by filtering 01f the salt or removal of the solvent by evaporation to dryness.

The following examples illustrate several specific emlbodiments of the invention:

EXAMPLE 1 The precursor olefin CF CF CF CH=CF is prepared by the dehydroiodination of the iodide The non-aqueous layer which separates after hydrolysis and addition of the sodium carbonate is the nitro alcohol CF CF CF CH(OH)CF NO having a boiling point of 52 C. at 44 mm. Hg and having a refractive index 11 1.3240. This nitro alcohol is obtained in about 40% yield.

Example 2 The precursor olefin c1=,c1= cr crr c1= c1 =cr= is prepared by the dehydroiodination of as described in the above mentioned copending application, Serial No. 53,878. A 50 gram portion (0.17 mole) of the olefin and 23 grams of N 0 are dissolved in milliliters of CF CICFCI according to the procedures described in Example 1. The mixture is placed in a 300 milliliter stainless steel autoclave which is sealed and then heated at 100 C. for 15 hours. The autoclave is then cooled to room temperature, vented, and the liquid contents poured into a Vigraux still where the excess N 0 and the chlorofluorinated solvent is distilled off leaving liquid product (92% yield).

The crude product is added to 200 milliliters of water, stirred and then the mixture made slightly alkaline by the addition of sodium bicarbonate. The mixture separates into an insoluble oil layer and an aqueous alkaline layer. The aqueous alkaline layer is first extracted three times with diethyl ether and the ether extract addedto the oil layer. The aqueous alkaline layeris then acidified with dilute hydrochloric acid and again extracted with diethyl ether. The ether extract is evaporated to give grams (19% yield) of a base-soluble yellow oil which crystallizes on standing, this being the a-hydroxy acid Recrystallization of this product from a benzene light petroleum ether solvent gives colorless needles, having a melting point of 82 to 83 C.

Analysis.Calculated for: C-7H F O C, 27.28; H, 1.63. Found: 27.00; H, 1.69. The infrared spectrum of this compound shows typical (OH) absorption at 2.88 and carbonyl absorption at 5.8 The compound is strongly' acidic and is an excellent surfactant in aqueous media as the free acid or in the form of its salts.

The water insoluble oil layer which separates during hydrolysis is dried and then evaporated to give 35 grams (59% yield) of a water-insoluble oil consisting of the nitro alcohol CF CF CF CH CF CH(OH)CF NO having a boiling point of 72. C. at 4 mm. Hg and a'refractive index n 1.3347.

16 grams of a Example 3 v The precursor olefin CF CH=CF in this sample is prepared by the dehydroiodination of CF CH CF I according to the procedures described in the aforementioned copending application, Serial No. 53,878. A solution of 27.6 grams (0.3 mole) of dinitrogen tetroxide in 100 milliliters of CF ClCFCl is placed a 300 milliliter stainless steel autoclave after which 26.4 grams (0.2 mole) of CF CH=CF is added by, vacuumtranster. The autoclave is then heated at'90 to 100 C. for 17 hours while shaking. The autoclave is cooled to room temperature and upon venting, 2.5 grams of unreacted olefin is'collected. The liquid product from the autoclave is poured into 100.rnilliliters of water which is stirred and then made slightly alkaline by the addition of sodium bicarbonate. The mixture separates into-an "oily water insoluble layer and an aqueous alkaline layer. The aqueous alkaline layer is extracted three times with diethyl ether after which it is acidified with aqueous HCl and then reextracted three times with additional diethyl ether. The ether extract from this second extraction is dried over andydrous magnesium sulfate and then evaporated to give grams of a base soluble oil consisting mainly of a hydrated form of the acid CF CH(OH)COOH, i.e. trifluoromethyl glycolic acid. Upon vacuum redistillation, this compound is found to have a boiling point of 57 C. at 123 mm. Hg.

Analysis.-Found: Fluorine 36.15; Neutralization equivalent 154. The infrared spectrum of'this compound (liquid film) has the following peaks: 3;(OH), 5.6-5.85n (C=O),'6.25 8.2a, 8.6;, 12.45;, l2.8p., 14.2,.

The water insoluble layer which separates upon hydrolysis, after drying and evaporation of the CF ClCFCl solvent is the constant boiling etherate of the nitro alcohol CF CH(OH)CF NO having the formula The precursor of olefin CF CH CF CH=CF in this example is prepared by the dehydroiodination of the iodide according to the procedures described in the above mentioned copending application, Serial No. 53,878. A 49 gram (0.25 mole) portion of the olefin and 32 grams (0.35 mole) of N 0 are dissolved in 150 milliliters of CF ClCFCl and the mixture dried over P 0 and then filtered into a 300 milliliter stainless steel autoclave. The autoclave is sealed and heated with shaking C. for 5 hours at a pressure of lbs./in. gage; The autoclave is then cooled and vented and the liquid content poured into water, stirred, after, which sodium bicarbonate is added until the solution is mildly alkaline.

A water insoluble oil layer separates from an aqueous alkaline layer. The aqueous alkaline layer is made acid by the addition of dilute hydrochloric acid and extracted with diethyl ether. After drying the ether extract over .anhydrous magnesium sulfate and evaporation of the ether, the hydroxy acid CF CH CF CH(OH)COOH is obtained.

The water insoluble oil layer separating upon hydrolysis is dried and after evaporation of the chlorofluorinated solvent there is obtained 21 grams of a yellow oil consisting of a nitro alcohol CF CH CF CH(OH)CF NO having a boiling point of 66 C. at 6 mm. Hg and a refractive is prepared by the dehydroiodination of according to the procedures described in the aforementioned applicationSerial No. 53,878. Following the procedure described in'Example 1, the olefin is reacted with a slight excess of N 0; in a sealed autoclave in as a solvent at a temperature of 100 C. for 20 hours.

The liquid contents of the autoclave are stirred in water;

a relatively strong acid having excellent surfactant properties in aqueous media.

zation is acidified and then extracted with CF ClCFCl Upon, evaporation of the extract the acid is obtained, a relatively strong acid having excellent surfactant properties in aqueous media.

Example 7 The ammonium salt of the hydroxy acid of Example 1 CF CF CF CH(OH)COOH is prepared by dissolving the acid in a large excess of CF ClCFC1 Gaseous ammonia is bubbled through the solution at room temperature until precipitation is complete. The CF ClCFCl solvent is removed by evaporation under vacuum to'provide the ammonium salt CF CF CF CH(OH)COONH a white crys talline solid.

Example 8 The sodium salt of the hydroxy acid of Example 2 CF CF CF CH CF CH(OH)COOH is obtained by adding sodium bicarbonate to the acid dissolved in an excess of diethyl ester. The salt a white crystalline solid, precipitates and is recovered by evaporation of .the ether to dryness.

The a-hydroxy acids of the invention are characterized by their chemical stability. In contrast to the hydrocarbon analogs which dehydrate readily to form the corresponding acrylic acids, the a-hydroxy acids of the invention are not subject to this type of dehydration. They are considerably stronger acids than their corresponding hydrocarbon analogs. They have excellent surface active properties, particularly when containing or more carbon atoms.

The compounds of the invention, as the free acid, or in the form of their salts, are useful as surfactants in aqueous media, particularly where the combination of good chemical stability and high surfactant activity is desired. In this respect, the compound of the invention RCF CH(OH) COOH and their salts where R is a perfluoroalkyl radical having from 2 to 12 carbon atoms are particularly valuable class because of the unusual surface properties conferred by the relatively long chain perfluoroalkyl group.

The compounds of the invention are also useful as chelating or sequestering agents, particularly in environments, such as strong oxidizing environments, where less stable materials such as the hydrocarbon a-hydroxy acids,

would be subject to a chemical attack and decomposition.

S We claim: 1. Compounds selected from the class consisting of fluorinated a-hydroxy acids of the formula RCF CH OH COOH and salts thereof selected from the class consisting of the alkali metal, calcium, magnesium, copper, iron, aluminum, chromium and ammonium salts, where R is a radical having from 1 to 20 carbon atoms selected from the class consisting of fluorine and perfluoroalkyl, perfiuorohydrowhere n is an integer from 1 to 8 and where R' is a perfluoroalkyl radical having from2 to 12 carbon atoms.

6. The fluorinated u-hydroxy .acid of the formula C F CH(OH)COOH 7. The fluorinated a-hydroxy acid of the formula C F CH CF CH(OH)COOI-I 8. The fluorinated a-hydroxy acid of the formula CF CH(OI-I)COOH 9. The fluorinated u-hydroxy acid of the formula CF CH CF CH (OH) COOH.

References Cited by the Examiner Chemical Abstracts, vol. 53, Formula Index, page 46F 1959 Grechishkin: Zhut. Eksptl. i. Teoret. Fiz., vol. 35, pages Simons: Fluorine Chemistry, vol. I, pages 483-5 (1950). Simons: Fluorine Chemistry, vol. II, page 393 (1950).

LORRAINE A. WEINBERGER, Primary Examiner.

LEON 'ZITVER, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,202,706 August 24, 1965 Murray Hauptschein et alm It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, lines 8 to 12, strike out "a radical having from 1 to 20 carbon atoms selected from the class consisting of fluorine and perfluoroalkyl, perfluorohydroalkyl, perfluorochloroalkyl and perfluorochlorohydroalkyl radicals." and insert instead selected from the class consisting of fluorine and perfluoroalkyl, perfluorohydroalkyl, perfluorochloroalkyl and perfluorochlorohydroalkyl radicals having from 1 to 20 carbon atoms.

Signed and sealed this 24th day of May 1966e (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. COMPOUNDS SELECTED FROM THE CLASS CONSISTING OF FLUORINATED A-HYDROXY ACIDS OF THE FORMULA 